Speaking in the Oval Office, President Barack Obama says Russia is "on the wrong side of history" in Ukraine and its actions violate international law. He says the US is considering economic and diplomatic options that will isolate Russia.

Washington — Secretary of State John Kerry’s emergency trip to Kiev Tuesday is meant to demonstrate resolute US support for the Ukrainian government in the face of Russia’s aggression and military occupation of the southern province of Crimea.

But for many Obama administration critics, Mr. Kerry’s trip should also be the occasion for President Obama to trash once and for all the “lead from behind” doctrine he debuted in the 2011 Libyan crisis.

The idea was that the United States, unable to take charge of every international crisis, would play a leadership role from the backseat by guiding and assisting other powers more directly implicated (geographically, economically, and in international security terms) in a crisis.

“The Obama administration must abandon its oxymoronic inclination to ‘lead from behind,’ ” says Andrew Kuchins, director of the Russia Eurasia Program at the Center for Strategic and International Studies in Washington. Absent strong American leadership in crafting “immediate” Western support for the interim Ukrainian government, Mr. Kuchins says, Russia will be tempted to “effectively separate” other eastern regions of the country from Kiev.

Suggesting that the whole world is watching how the US responds to Russian action in Ukraine, Kuchins says American credibility is on the line globally. Allowing a “takeaway” from the Ukraine crisis that the US is unwilling to stand up to violations of a country’s sovereignty could have disastrous implications in Asia, for example, where he notes China and Japan are locked in a worrisome territorial dispute.

Others say Russian President Vladimir Putin in particular took Mr. Obama’s unwillingness to intervene in Syria as a sign that the US under Obama would not challenge Russian action in Ukraine.

“Ukraine is evidence of the total failure of the Obama doctrine that America leads by leading from behind,” says Steven Bucci, director of foreign and national security policy studies at the Heritage Foundation in Washington.

The way Obama backed away last summer from threatened intervention in Syria – by accepting a Russian deal for ridding Syria of chemical weapons – convinced Mr. Putin he had “leeway” to take action in Ukraine that would not meet stiff resistance from the US, Mr. Bucci says.

Allowing someone like Putin – determined to preserve what he can of Russian influence in the former Soviet space – to act aggressively with no real consequences can only lead to one thing, Bucci says: “He’s going to take more” advantage of the freedom to act that he senses from the US and other Western powers.

It was not clear Monday what concrete measures of support for Ukraine Secretary Kerry would take with him to Kiev. In a round of television appearances Sunday, Kerry set a tone that was considerably harsher toward Russia than that of the White House so far. He said the occupation of Crimea was a ‘brazen act of aggression,” and further labeled it “a stunning willful choice by President Putin.”

On the eve of Kerry’s Kiev trip, his spokeswoman said Monday that the US is moving quickly toward sanctions against Russia unless its troops leave Crimea.

“We are not just considering … it is likely we will put [sanctions] in place” without some sign of Russian retreat, State Department spokeswoman Jen Psaki said. “We are preparing options and we are likely moving down that path.”

Kerry said Sunday that Russia risked being hit with trade sanctions, while Russian individuals with assets in the US could find those assets frozen.

By keeping his troops in Crimea, Putin would doom this summer’s G8 meeting that the Russian leader had planned to host in Sochi, Kerry said. Russia could even find itself kicked out of the G8, the elite club of global industrial powerhouse democracies, he added.

Among Kerry’s options on his trip, he could offer some immediate economic support for the crisis-laden government of President Oleksandr Turchynov and Prime Minister Arseniy Yatsenyuk.

But perhaps even more important than whatever bilateral measures Kerry might offer is for the US to demonstrate leadership of the Western response to Russia, some Atlantic Alliance experts say.

“This is a moment for American leadership. The Europeans have always tended to stand back and wait for the Americans to come forward and lead, and this is certainly one of those times,” says Nile Gardiner, an expert in transatlantic relations at Heritage. The French and German responses to Russia’s actions “have been pretty disquieting,” he says, while Britain’s reaction has “not been particularly robust, either,” he adds.

Germany sought to stick a pin in Kerry’s trial balloon about expelling Russia from the G8, with German Foreign Minister Frank-Walter Steinmeier on Sunday cautioning that such a move would be counterproductive because it would eliminate the one venue for direct West-Russia dialogue.

Indeed, Europe’s major powers all appear to be more focused than the US so far on maintaining a “dialogue” with Russia over its aggression. That may be a reflection of the fact that Russia is the European Union’s third-largest market for its products after the US and China, some economists say, and that Russia is a crucial energy source for the EU.

But others say the Ukraine crisis is about much more than economics but is about a broader Europe’s transition and the political model it follows. The outcome will have lasting implications for NATO and the transatlantic alliance, these experts say – and that puts Obama, as the unrivaled leader of NATO, unavoidably at the helm in addressing the crisis.

What Ukraine could effectively mean for Obama, they say, is an end to the idea of leading from behind.